How-To Get Tanked Up with POR15 Fuel Tank Sealer

There's been a good bit of progress on Project 13/30 over the past month, but to look at it you'd struggle to tell exactly where. Still, it's happened, and I know 'cos I was there. With the BMR subframe connectors welded in and the shell now turned upside down on the rotisserie, I addressed the rear wheel tubs. The Eastwood chassis black that coats the underside should offer plenty of protection but I figured that you can't have too much rustproofing, so I grabbed the Rustbuster Epoxy Mastic (1). This is a two-part paint plus a thinner if needs be, so I mixed it 50/50 and then added a drop of thinner because it was cold. Plastic measuring jugs like these (2) from Wilkinson's cost about 30p and are just the job. I coated the whole rear arch on both sides, plus a couple of the seams (3).

This stuff's great, but I'd forgotten just how much it smells like a cat litter tray, and just how powerful the fumes are!

I also broke out the Tetrosyl Stone Chip for the bottom of the sills. This is another thick paint designed to bounce the gravel right off, so I masked off the underside of each sill and gave it a coat (4). It's designed to be overpaintable, but this strip is out of sight anyway.

I turned my attention briefly to the axle casing, which I want to send away for media blasting. I wanted to remove the bushes that attach the upper arms to the diff housing (5), but they're not keen to shift. I jury-rigged a bearing puller out of an old Cortina void bush removing tool (ask any long serving mechanic about Cortina void bushes and watch them shudder) and the collar from a FWD car's front wheel bearing outer race, but even with some persuasion from a blowtorch (6) and subsequent small fire, they refused to budge. I may actually have to get the correct tool for the job.

In the meantime, I flipped the axle around and removed the rear cover to take a look inside (7).

It appears that these 8.8” axles didn't have a gasket on the rear cover; instead they relied on a bead of silicone sealant (8), which seems to me to be asking for trouble. The diff looked to be in good order, a 2.73:1 ratio TractionLok unit, although someone had removed the centre pin that holds the spider gears (9). Not to worry, as with a bit of luck the diff unit will get replaced anyway. I unbolted the carrier bearings (10) and lifted the diff unit out (11) after loosening it with a gentle nudge from a long bar. On either side of the diff is a carrier bearing and a shim or shims. It's crucial to make sure these shims go back to the same place they came from, so I attached the shims, bearing races and bearing cap to the correct side of the diff unit with cable ties (12), then wrapped the whole thing in plastic for storage.

Then I turned my attention to the fuel tank, which required removing it from the donor car, which is outside and … oh, super, it's dark and belting with rain. To get to the fuel tank I first had to remove the towbar (13) then undo the nuts holding the filler neck to the body inside the fuel filler door (14).

Then I crawled under the car and, my God, I can't believe just how quickly it's rusting! It's just dissolving before my eyes; one of the reasons I'm so keen to rustproof Project 13/30 to the best of my abilities. I put a trolley jack under the centre of the tank, took the weight, and undid the bolts holding the tank straps (15).

One undid fine, the other snapped the little hook-end from the captive nut just to make life difficult. I then used a small screwdriver to drift the pins out of the other end of the straps (16), which is tricky in broad daylight at head height; in the dark, on your back, in the rain, it's a real test of your patience.

With the straps out of the way, it's then just a case of slowly lowering the jack whilst wiggling the tank free of the filler neck (17). Mind you don't bust the rubber grommet where the filler goes into the tank – they're quite expensive to replace. With the tank on the floor, you can undo the fuel feed and return lines and the wiring to the fuel pump (18), all previously bodged, then drag the tank out (19). Considering it's completely bare steel, the tank seems to have survived quite well.

The tank sits in a protective plastic tray, so with that out of the way (20) I could remove that expensive rubber filler neck grommet (21), the vapour line bung (22), the fuel pump (23) and the fuel level sender.

The latter two are secured by a metal ring that you have to carefully tap round with a hammer and punch, but watch out for the rubber O-ring seal underneath.

I emptied the tank of any remaining fuel (which I then put into the Lexus – hey, waste not want not) and gave it a damn good rinsing out with the hose (24) in preparation for its POR- 15 tank sealant. This comes as a three-part kit, and is pretty labour intensive but very worthwhile. To begin with, you need to seal up all the holes, for which I used duct tape (25), then make a 50/50 mix of their POR-15 Cleaner Degreaser(26) and warm water. I poured this into the tank through the vapour line bung hole (27) and plugged it, then you need to shake it all around, rotating the tank occasionally to make sure it gets into all the corners, for at least 20 minutes. Then unplug one of the holes, tip it out and give it a rinse. The next step is POR-15 Metal Prep(28), a pre-primer that cleans all the residues out and lays down a zinc phosphate layer. Again, you plug the tank back up, add the neat Metal Prep(29), rotating the tank so the liquid is sitting on each surface for 20 minutes – six sides to the fuel tank means two hours.

While all this was going on, I disappeared back under the donor car for the fuel filter and bracket. Having prized the horseshoe clip from the union between the return hose and the return pipe, I gently tried to pull it off and … snap (30).

The rusty steel return pipe just crumbled, and a chunk of it came away with the rubber pipe. The bracket that holds the filter was pretty crusty but looked like it'd clean up okay, but then I noticed that there were no bolt holes for it on the shell (31). Well, of course, there wouldn't be, would there? The shell is an '83, before they'd switched to fuel injection! This wouldn't be the last time an issue like this cropped up.

The Metal Prep was due to come out of the tank right about now, so I drained it back into the bottle (32) – it's reusable – and rinsed the tank out again with warm water. The tank needs to be bone dry before the next step, so I went down to the nearest Screwfix and treated myself to a hot air gun for £11, returned, removed all the duct tape plugs, and set the tank to drying (33). Although it's difficult to see into the tank, I could just see that there was still moisture trapped in the seam – this tank, like most tanks, is made from a top half and a bottom half pressed and welded together, so there's a big seam running all the way around the middle. I chased the damp out by heating up the seam on the outside (34).

Then it was time for the last step – the POR-15 Fuel Tank Sealer(35). The instructions say to stir the can until a uniform colour is achieved, and while it's very attractive watching the black and silver kaleidoscope effects, it did take around 15 minutes to achieve. I then bunged all the holes back up, and poured the sealer into the tank (36). Again, you have to make sure that the sealer coats every inch of the inner surface of the tank, so having a Workmate bench upon which to clamp the tank at odd angles is a real help. Then, when your time is up, you pour it all out again – I poured the whole can in, and about three quarters of it came back out again. There's nothing you can do with the leftovers, you just have to wait for it to set then throw it away, which seems a shame.

The following day, I checked the inside of the tank with a torch, and it seems I had managed to get a full coating. It's a full day job to do it properly – two doses of Cleaner Degreaser, one dose of Metal Prep and one dose of Fuel Tank Sealer – but that's about two hours of work and four or five hours of sitting around in between, so you can get on with other stuff. Anything that stops the tank rusting and silting up the fuel lines, and prevents the ethanol in fuel corroding the tank, is fine by me, so I consider it a job well done.

There's plenty more Project 13/30 work on the way, so stay tuned for next month when we'll hopefully get started on the plumbing.